All terrain vehicle

ABSTRACT

A high speed all terrain vehicle of the type having four wheel drive through a limited slip inter-axle differential that is effective to transfer driving torque between a front differential and a rear limited slip differential upon loss of traction of some of the wheels. Improved rough terrain mobility is achieved through an independent torsion bar suspension employing a power augmented roll steer characteristic to reduce the turning radius of the vehicle.

United States Patent 1 Hickey 1 1 Jan. 9, 1973 541 ALL TERRAIN VEHICLE3,105,699 /1963 Peras ..280/96.2 R

[75] Inventor: Victor F. Hickey, Ventura, Calif. OTHER PUBLIC [73]Asslgnee: FMC Corporation San Jose Cahf' Publication: Suspensions fromthe Ground Up By [22] Filed: Oct. 16, 1970 Charles M. Rubly, S.A.E.Publication, March -17,

1960, 143D pages 4-7. [2}] Appl' 81236 Hot Rod" Magazine, issue of Nov.1968, pages 104-105. [52] US. Cl. ..180/44 R, 180/73 D Publication:Suspensions from the Ground Up by [51] Int. Cl. ..Bk 17/34 Charles M.Rubly, Soc. Auto. Eng. Publication, March [58] Field of Search....180/44 R, 42, 73; 280/962 R, 15-17, 1960, 143D, pages 4 to 7.

Primary Examiner-Kenneth H. Betts [5 6] References Cited Attorney-F. W.Anderson and C. E. Tripp UNITED STATES PATENTS [57] ABSTRACT 1,780,37011/1930 Tenney ..180/44 R X 2,092,612 9/1937 Olley ..280/96.2 R x ASpied term i i i type 2 631 681 3/1953 Utz et al 180/44 R wheel drivethrough a hmlted shp inter-axle d1f- 2978255 4,1961 ggi: 12 A ferentialthat is effective to transfer driving torque 3:235:021 2 19 Hm 1 0 44 Rbetween a front differential and a rear limited slip dif- 3,246,7174/1966 Dreisziger ..180/73 R ferential upon loss of traction of some ofthe wheels. 3,277,975 10/1966 Van Winsen.. ..l/73 R improved roughterrain mobility is achieved through 3,379,269 4/1968 Zetye ..l80/73 Ran independent torsion bar suspension employing 3 3,390,593 7/ 1968Brownyenn "/44 Rx power augmented roll steer characteristic to reduce3,407,893 10/1968 Hill et al. ..180/44 R the turning radius of thevehicle 3,451,497 6/1969 Barnes et al ..180/73 t 1 Claim, 7 DrawingFigures PATENTEDJAM 9.197s

SHEEI 1 OF 3 mm mm 9 6 00.

INVENTOR. VICTOR F. HICKEY ATTORNEYS PATENTEU JAN 9 i973 SHEET 2 [IF 3PATENTEIJJAN 9 I975 SHEET 3 [IF 3 ALI. TERRAIN vsurcus BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention pertains towheeled crosscountry rough terrain vehicles and more particularly tosuch vehicles having four wheel drive, independent suspension with rollcenter steering and torsion bar springing.

2. Summary of the Invention The purpose of the present invention is toprovide a wheeled high speed, cross-country, rough terrain vehiclesuitable for use as a reconnissance vehicle for use with highly mobilearmored forces or for use as'a family recreational vehicle. Thepresently known vehicles are not capable of operating with modernarmored forces at sufficiently high speed and safety in rough terrainconditions.

The vehicle of the present invention achieves this higher mobilitythrough a novel drive train that takes power from the transmission anddivides it between a front differential and a rear limited slipdifferential by means of an interaxle differential that incorporates alimited slip features in both forward or reverse. This drive trainsupplies a four wheel drive to the vehicle in which motive power isavailable as long as either one of the rear wheels has traction.

Mobility is further improved by combining the four wheel drive trainwith a fully independent suspension employing adjustable torsion barspringing and coil springs over shock absorbers providing: a low profileand increased visibility over the front of the vehicle, a large wheeldisplacement for rough terrain, and a capability of adjusting thevehicle height for varying the ground clearance.

A further advantage resides in the employment of power augmented rollcenter steering at the rear wheel which permits higher speed turns at adecreased turn radius.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is, a diagrammatic perspectiveview of the vehicle of the present invention showing the four wheeldrive power train.

FIG. 2 is a'view similar to FIG. 1 showing the vehicle frame andsuspension.

FIG. 3 is an enlarged perspective view of the left rear wheelsuspension.

FIG. 4 is a section taken on line 44 of FIG. 3.

FIG. 5 is an enlarged view of the torsion bar mounting and anchors.

FIG. 6 is a diagrammatic end view of the rear suspension.

FIG. 7 is a diagrammatic plan view of the vehicle showing the effect ofroll center steering.

DESCRIPTION OF THE INVENTION The all terrain vehicle of the presentinvention is Drive Train Included in the drive train 16 is an interaxledifferential 20 which divides the power from the transmission 14 to afrontpropeller shaft 22 and a rear propeller shaft 24. A conventionalconstant velocity double universal joint 26 such as the I-Iookes type isemployed to connect the propeller shaft 22 to the interaxle differential20, while a single constant velocity universal joint 28 connects thepropeller shaft to a front differential 30. This differential is of awell known type such as employed in a 1970 Corvette automobile and hasan input-output ratio of 5:14 to 1:00. The construction of thedifferential 30, while not important to the present invention, isdescribed in the i970 Chassis Service Manual No. ST 130-70 pages 4-23through 4-25 and FIG. 65 thereby published by the Chevrolet MotorDivision, General Motors Corporation, Detroit, Michigan, United Statesof America.

From the front differential 30, the front wheels 18 are driven by driveshafts 32 that have single, constant velocity universal joints 34 of theRzeppa or Bendix- Weiss type at each end.

y In order to supply power to the rear wheels 18', the rear propellershaft 24 is connected between a rear differential 36 and the interaxledifferential 20 by means of single, constant velocity universal joints38. A pair of rear drive shafts 40 (shown only on one side) havingRzeppa types of single, constant velocity universal joints 42 at theirends, distribute the power to the rear wheels I8.

The rear differential 36 is of the limited-slip type capable oftransferring torque from one rear wheel to the other when there is adecrease or loss of traction on one side. The rear differential 36employed in the vehicle is a I970 Corvette positraction" differentialhaving a 5:14 to 1:00 ratio. For a description of this differentialreference may be made to the 1970 Chassis Overhaul Manual No. ST l3l-70pages 4 l 1 through 4 19 and 4 26 through 4 29 published by theChevrolet Motor Division, General Motors Corporation, Detroit, Michigan,United States of America.

shown in FIG. 1 where the body 10 of the vehicle is 1 The interaxledifferential20 as previously mentioned serves to divide the power fromthe transmission 14 to the front and rear propeller shafts 22 and.24.The interaxle differential further incorporates a limited slip featuresimilar to the rear differential 36 such that when either the frontwheels 18 or rear wheels 18' are subjected to reduced traction or a lossof traction, torque from the transmission is directed to the other setof wheels (either front or rear) and is effective when the vehicle isdriven either in forward or reverse. Such an interaxle differential isproduced by the Warner Gear/Wamer-Motive Divisions of the Borg-WarnerCorporation. The limited slip interaxle differential 20 is constructedin accordance with the principles of Brownyer US. Pat. No. 3,380,593,issued July 2, 1968 which normally drives both output shafts with equaltorque Suspension Referring now to FIGS. 2 and 3 and particularly toFIG. 3 it can be seen that the frame 10 of the vehicle is of a weldedtubular construction. Each of the four driving wheels, mounted to thecomers of the frame by independent suspension units are indicatedgenerally at 44 These suspension units are substantially similar exceptfor variations in torsion bar, shock absorber and linkage attachmentpoints due to the'units'location, i.e., front to rear and side to side.

A typical suspension unit 44 such as the left rear unit is shown in FIG.3. The unit generally comprises an upper Aframe arm 46 and a lower Aframe arm 48. These frames are attached to longitudinally extendingtubular frame members 50 by means of multiple brackets 52. The innerends of the A frame arms usually include bonded rubber bushings 54 whichreceive mounting bolts 56 that secure the'A frames to the brackets 52while permitting vertical swinging motion of the A frames 46 and 48. Asteering knuckle 58 is mounted between the outer ends of the A frames at60 by means of conventional ball mounts best seen in FIG. 4.

The steering knuckle 58 includes a spindle 62 having a bearing mountedwheel hub 64 that has wheel mounting studs 66 and an attached brake disc68. A brake caliper 70 which extends over the-disc is also attachedtothe knuckle 58 and is effective to brake the wheel when hydraulicpressure is applied. The suspension unit further includes an anti-swaybar 72 that extends transversely across the rear of the frame and-isattached thereto by means of rubber bushed mounts 74 (only onebeingshown). The ends of the sway bar are at tached to the lower A framearms 48 by means of a bolt and rubber cushion connector indicated at 76in FIG.

tie rod 78 pivotally attached between the frame 10 and an arm 79 on thesteering knuckle 58 by means of ball joint mounts 80. As seen in FIG. 7the front suspension units also have arms 79 to which a wellknownAckerman type steering linkage is attached at 81.

Referring nowto FIG. 3, a coil over a tubular double acting shockabsorber 82 is pivotally-supported on its upper end to a diagonal framemember 83 between a pair of brackets 84. The shock absorber 82 extendsdownwardlybetween the wishbonearmsof the upper A frame 46. The lower endof the shock absorber is at- .The rear suspension unit also includes anadjustable tached to the lower A frame arm 48 by means, of a rubberhushed bolted connection 85 best seen in FIG.

FIG. 4. A similar torsion bar 86 extending horizontally of the vehicleis provided for each suspension unit as seen in FIG. 2. Theother ends ofthe torsion bars are adjustably attached to the vehicle frame by meansof torsion bar anchors 88. Referring now to FIG. 5, anchors 88 fit overhexagonal ends of the torsion bar. These anchors are longitudinallyrestrained in box section brackets 90 welded to the frame 10. In orderto rotatably restrain the anchors 88 and permit adjustment of thepreload on the torsion bars for the purpose of varying thevehicle groundclearance and spring rate, a threaded adjusting bolt 92 passes through aclearance hole in the bracket 90 and through a threaded stop bar 94 tobear against the anchor at 96. To locate the stop bar 94 and prevent itsrotation when bolt 92 is turned,

an aperture 98 is provided in the bracket through which the stopprojects.

Each of the suspension units 44 mounts a 16 inch diameter by 10 inchwide rim 100 (FIG. 2) upon which low pressure tires I02 (15 p.s.i.)prcferrably size 36 X 12.4 X 16.1 are mounted.

Roll Steering As a result of the independent suspension having unequal Aframe arms 46 and 48 and the tie rods 78 between the steering knuckle 58and frame, the vehicle and in particular the rear wheels I8exhibit thecharacteristics known as roll steering. This characteristic is usuallyintentionally eliminated in most vehicles including cross-country typesby the selection of the suspension geometry. The vehicle of the presentinvention employs power augmented roll steering to improve cross-countrymobility, using the characteristic at the rear wheels to decrease thevehicle turning radius. The roll steering characteristic and itsemployment and effect on vehicle turning radius will now be describedwith reference to FIGS. 6 and 7. As seen in FIG. 6, an end view of therear of the vehicle, when the frame 10 of vehicle rolls outwardly asindicated by arrow 104 due to a right hand turn, the rear wheels 18'also leanoutwardly. This is due to the fact that the center of gravity106 of the body is above the roll steer center 108, and the fact thatthe upper A frame arm 46 is shorter than the lower frame arm 48. Thepresent suspension allows a maximum body roll in the order of 834 andproduces a corresponding outward tilt on each rear wheel in the order of6", as seen in FIG. 6.

Referring now to FIG. 7, a diagrammatic plan viewof the vehicle making aright hand turn, it can be seen that the rear wheels I8 also turntogether toward the outside of the turn approximately 256 as well astilting as in FIG. 6.'The turning of the rear wheels I8 through i thehorizontal angle of 295 is caused by an inward pull on the left rear tierod 78 and an outward push on the right rear tierod due to rotation ofthe vehicle frame 10 about its roll center. This is seen as the motionbetween the normal'tie rod-position shown in broken line and thedisplaced position in solidline shown in FIG. 6.

The outward turning of the rear wheels 18 and the application of powertothem through the limited slip interaxle differential 20 produces a poweraugmented roll steer that in turn reduces the turn radius of thevehicle. 4

The front wheels 18 exhibit the same roll steer characteristic with theAckerman type steering linkage 81 taking the place of the tie rods 78 atthe rear suspension. Although the roll steer characteristic tends toincrease the turning radius of the front wheels, this is easily overcomeby turning the steering wheel further. 2

Operation In cross-country operation'the vehicle is driven as a normalautomobile. The four wheel drive power train 16 (FIG. I) is always inthe f four wheel mode, not being selectively engagable as in the Jeeptype vehicles. If traction is lost on either of the front wheels 18, notorque will be delivered to the other front wheel since they are driventhrough the'common slip-type front dif-' ferential 3 0. Thereaftertheentire torque from the transmission 14 is transferred tothe reardifferential 36 through the limited slip interaxle differential 20. Nowif either of the rear wheels loses traction, the entire torque istransferred to the other rear wheel due to the limited slip action ofthe rear differential 36. Thus it is possible to drive the vehiclehaving traction at only one of the rear wheels.

In the case of loss of traction at both rear wheels 18 the interaxledifferential 20 transfers thetorque to the front differential 30 todrive the front wheels 18 until either of them lose traction.

Employing the present four wheel drive train with a fully independentsuspension, roll center steering, adjustable torsion bars for varyingthe vehicle ground clearance as well as suspension spring rate, in avehicle with a dry weight of 4500 lbs., a wheel base of 114 inches and atrack of 62 inches results in an all terrain vehicle capable of safelymoving across rough terrain at speeds approximately twice as great ascurrent Jeep type vehicles.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

lclaim:

l A four wheeled, front wheel steering, all terrain vehicle comprising aframe, an engine and transmission mounted on the frame, means forindependently suspending all four wheels, a limited slip differentialand articulated axle drive for the rear wheels, a free runningdifferential and articulated axle drive for the front wheels, a limitedslip interaxle differential which normally drives each output shaft withequal torque driven by said transmission, and drive shafts running foreand aft and substantially concentrically from said interaxledifferential to said wheel differentials.

1. A four wheeled, front wheel steering, all terrain vehicle comprisinga frame, an engine and transmission mounted on the frame, means forindependently suspending all four wheels, a limited slip differentialand articulated axle drive for the rear wheels, a free runningdifferential and articulated axle drive for the front wheels, a limitedslip interaxle differential which normally drives each output shaft withequal torque driven by said transmission, and drive shafts running foreand aft and substantially concentrically from said interaxledifferential to said wheel differentials.